The present invention relates to a method for the elimination of foam formation in chemical processes and in particular, to the elimination of foam formation in leaching of an ore concentrate in heated concentrated sulphuric acid by using microwaves to raise the temperature of the slurry.
Many procedures, generally multi-step processes, have been developed to extract valuable commodities from crude ore. Chemical extraction processes comprise a series of steps in which the ore concentrate is treated with various reagents under specific conditions to selectively extract the values contained therein. In such chemical extraction processes, there are steps which include leaching the ore concentrate in corrosive solutions such as sulphuric acid. These reactions may produce gaseous products which may in turn form a corrosive foam above the slurry. This foam can cause serious operational problems, in particular, enhanced corrosion of the reaction vessels. In the production of beryllium hydroxide from ore concentrate, for example, the ore is treated with concentrated sulphuric acid at 240.degree. C. This treatment produces gaseous products, namely, carbon dioxide and silicon tetrafluoride which produce a foam above the slurry. The foam is generally controlled by the addition of defoaming agents and/or controlled heat input.
The method of the subject invention provides the novel step of heating the mixture by microwaves to control and eliminate the formation of a foam. This method eliminates the need for defoaming agents and/or controlled heat input.
In U.S. Pat. No. 4,582,629, Wolf discloses the use of microwaves in enhancing the separation of an oil/water emulsion. Although, in principle, there are similarities, between emulsions and foams, as pointed out by A. Prins, in "Advances in Food Emulsions and Foams" (Dickinson and Stainsby, Elsevier Applied Science) at pages 91-92, there are several quantitative differences between them, from a physical standpoint.